1. Field of the Invention
The present invention relates to an electron emitter having a first electrode and a second electrode that are disposed in an emitter.
2. Description of the Related Art
Recently, electron emitters having a cathode electrode and an anode electrode have been finding use in various applications such as field emission displays (FEDs) and backlight units. In an FED, a plurality of electron emitters are arranged in a two-dimensional array, and a plurality of phosphors are positioned in association with the respective electron emitters with a predetermined gap left therebetween.
Conventional electron emitters are disclosed in Japanese Laid-Open Patent Publication No. 1-311533, Japanese Laid-Open Patent Publication No. 7-147131, Japanese Laid-Open Patent Publication No. 2000-285801, Japanese Patent Publication No. 46-20944, and Japanese Patent Publication No. 44-26125, for example. All of these disclosed electron emitters are disadvantageous in that, since no dielectric body is employed in the emitter, a forming process or a micromachining process is required between facing electrodes, a high voltage needs to be applied to emit electrons, and a panel fabrication process is complex and entails a high panel fabrication cost.
It has been considered to make an emitter from a dielectric material. Various theories about the emission of electrons from dielectric materials have been presented in the following documents: Yasuoka and Ishii, “Pulsed Electron Source Using a Ferroelectric Cathode”, OYO BUTURI (A monthly publication of The Japan Society of Applied Physics), Vol. 68, No. 5, pp. 546-550 (1999), and V. F. Puchkarev, G. A. Mesyats, “On the Mechanism of Emission from the Ferroelectric Ceramic Cathode”, J. Appl. Phys., Vol. 78, No. 9, 1 Nov., 1995, pp. 5633-5637, and H. Riege, “Electron Emission from Ferroelectrics—A Review”, Nucl. Instr. and Meth. A340, pp. 80-89 (1994).
As shown in FIG. 51 of the accompanying drawings, a conventional electron emitter 200 has an upper electrode 204 and a lower electrode 206 mounted on an emitter 202. The upper electrode 204, in particular, is disposed in intimate contact with the emitter 202. An electric field concentration point is provided by a triple point including the upper electrode 204, the emitter 202, and the vacuum. In this case, the peripheral edge of the upper electrode 204 serves as the electric field concentration point.
However, since the peripheral edge of the upper electrode 204 is held in intimate contact with the emitter 202, the degree of the electric field concentration is small, and the energy required to emit electrons is low. Since electrons are emitted from a region that is limited to the peripheral edge of the upper electrode 204, the electron emitter 200 suffers variations of overall electron emission characteristics, making it difficult to control the electron emission, and has a low electron emission efficiency.